I’m glad this lights casing was earthed!

Yet another LED floodlight that I ordered at the same time as the others, but this one took a while to arrive with it’s SPECIAL surprise.
I checked the earth connection to the case and it was fine. That’s a good start. I powered it up and the RCD (GFI) that covers my whole home tripped.
I reset the breaker and did an insulation test between live and ground and got an odd reading of just over 1 Megohm (not enough to trip the earth leakage detection alone).
On internal examination I found the output of the PIR sensor had its crimp connection sandwiched between the case and cover and the metal sealing rib had sliced through to the live metal. This explains why the insulation test didn’t detect the real fault (PIR sensors relay not activated) and suggests the odd resistance reading was probably a convoluted path through the PIR power supply circuitry to the neutral, and then through the LED drivers primary circuitry to the switched live and earth.
I’m really glad the case was earthed, as otherwise the fitting would have worked as normal, but its case would have been live at 240V whenever the lamp switched on.
On a plus note, the case IS grounded and the power supply IS rated 10W.